Siren



FIG. 1 is a top plan view of a siren showing my new design.

FIG. 2 is a front elevational view thereof;

FIG. 3 is a left side elevational view thereof;

FIG. 4 is a right side elevational view thereof; and

FIG. 5 is a bottom plan view thereof;

The front elevational view and the rear elevational view (now shown) are identical. 

The ornamental design for a siren, substantially as shown and described. 